Four radio resource control (RRC) states are defined in the conventional third generation partnership project (3GPP) specifications. Those RRC states are CELL_DCH state, CELL_FACH state, CELL_PCH state, and URA_PCH state. Improvements on the conventional CELL_FACH and CELL/URA_PCH states have been introduced to the 3GPP specifications to enhance the overall quality of experience (QoE) perceived by end users. The CELL_FACH and CELL_URA_PCH improvements attempt to reduce state transition delays and overall signaling latencies by using high speed downlink packet access (HSDPA) resources in the CELL_FACH and CELL/URA_PCH states.
With an introduction of the enhanced CELL_FACH state, a high speed downlink shared channel (HS-DSCH) may be used in the CELL_FACH state. The HS-DSCH replaces the conventional forward access channel (FACH). A wireless transmit/receive unit (WTRU) with enhanced FACH capability will receive downlink messages over the HS-DSCH. For example, downlink RRC messages, (e.g., CELL UPDATE CONFIRM and URA UPDATE CONFIRM messages), will be sent to the WTRU over the HS-DSCH in the CELL_FACH state.
With an introduction of the enhanced CELL/URA_PCH states, the HS-DSCH may also be used in the CELL_PCH and URA_PCH states. The HS-DSCH replaces the conventional FACH and PCH, and dedicated control channel (DCCH) and dedicated traffic channel (DTCH) may be transmitted to the WTRU in the CELL_PCH state over the HS-DSCH. A WTRU with enhanced PCH capability will receive paging messages over the HS-DSCH when in CELL/URA_PCH states.
The WTRU may autonomously transition from the CELL_PCH state to the CELL_FACH state if the WTRU has uplink data or signaling to transmit. Multiple discontinuous reception (DRX) cycle may be defined in the CELL_PCH and URA_PCH states, which is a power saving mechanism that allows the universal terrestrial radio access network (UTRAN) to quickly access low activity WTRUs.
A WTRU or network that supports enhanced PCH has to also support enhanced FACH. However, the WTRU or network may support enhanced FACH without supporting the enhanced PCH. Therefore, when a WTRU triggers a UTRAN routing area (URA) update and both the WTRU and the network support enhanced FACH but not enhanced PCH, a URA UPDATE CONFIRM message will be received over the HS-DSCH but the WTRU will receive the paging message over the PCH. However, when the WTRU supports enhanced PCH, both the URA UPDATE CONFIRM message and paging messages are received over the HS-DSCH.
For paging in the CELL/URA_PCH states, a 3GPP Release 7 WTRU monitors a paging indicator channel (PICH), similar to 3GPP Release 6. Once a paging indication is detected, the WTRU monitors the HS-DSCH for reception of the paging control channel (PCCH) frame rather than monitoring the PCH/secondary common control physical channel (S-CCPCH).
When selecting a cell, a Release 7 WTRU determines if the cell supports enhanced FACH based on the configuration information that is broadcast on the broadcast control channel/broadcast channel (BCCH/BCH). More specifically, a system information block (SIB) Type 5/5bis includes two information elements (IEs): “HS-DSCH common system information” and “HS-DSCH paging system information”. These IEs provide configuration information necessary for the WTRU to receive HS-DSCH in the CELL_FACH, CELL_PCH and URA_PCH states.
A WTRU determines support for HS-DSCH reception in the CELL/URA_PCH states based on the configuration information that is broadcast in the cell on the BCCH/BCH. If the HS-DSCH paging system information is present in SIB 5/5bis, the WTRU configures itself for reception over the HS-DSCH rather than the PCH/S-CCPCH.
However, a drift radio network controller (DRNC) is not fully aware of the WTRU capabilities when in the CELL_PCH state. When the CELL UPDATE message is sent to the DRNC, the WTRU only indicates whether it supports the enhanced CELL_FACH state. A WTRU with enhanced CELL_FACH capabilities has an option of supporting HS-DSCH reception only in the CELL_FACH state or HS-DSCH reception both in the CELL_FACH and CELL/URA_PCH states. This is not indicated in the CELL UPDATE message and thus the DRNC does not know how to page the WTRU. If a serving radio network controller (SRNC) attempts to page the WTRU using the paging type 1 mechanism, the DRNC does not know which channel the WTRU monitors for paging, (i.e., HS-DSCH or PCH/S-CCPCH).
When the WTRU is in the URA_PCH state, the DRNC is unaware of the WTRU's capabilities unless explicitly indicated by the SRNC. The SRNC might not indicate the WTRU capabilities, (i.e., enhanced CELL_FACH capabilities), to the DRNC if the WTRU in the URA_PCH state is paged by the SRNC and has roamed to the cell without having performed UTRAN registration or cell update, or if the WTRU is connected to a Release 6 SRNC and roams to a Release 7 cell in the network.
In the first case, the SRNC sends a PAGING REQUEST message over Iur to an RNC that controls the cells in the UTRAN registration area (URA) group. However, the DRNC is unaware of which paging channel the WTRU is monitoring, (i.e., HS-DSCH or PCH/S-CCPCH). The DRNC is unaware of the WTRU capabilities unless the WTRU has performed a URA update at an earlier time in one of the cells that are controlled by the RNC. As such, the DRNC may page the WTRU over HS-DSCH in all cells that support paging over HS-DSCH. However, if the WTRU does not support HS-DSCH reception in the CELL_PCH state, the WTRU will never receive the paging indication. The DRNC may page the WTRU over PCH/S-CCPCH. However, if the WTRU and the cell both support HS-DSCH reception in the CELL_PCH state, the WTRU will never receive the paging message as it is monitoring HS-DSCH instead of PCH.
In the second case, a Release 7 WTRU roams to a Release 7 cell within the same URA, while connected to a Release 6 SRNC. The WTRU will monitor HS-DSCH for paging because the HS-DSCH paging system information is broadcast in the cell. However, the Release 7 DRNC is unaware of which channel the WTRU is monitoring for paging messages since the DRNC does not have any knowledge of the WTRU capabilities.
In addition, in the case where the WTRU does not support enhanced PCH but supports enhanced FACH, if a URA UPDATE is triggered and the CRNC is not aware of the WTRU capabilities it will not know over what transport channel to send the RRC messages, (e.g., URA UPDATE CONFIRM message).